Electrodeposition of bright cobalt plate

ABSTRACT

A method to extend the bright plating range obtained with obenzoyl sulfimide as the principle Class I brightener in acidic cobalt plating baths containing at least 90 percent by weight cobalt down into the very low current density areas or recesses by the use of bath-soluble organic sulfide compounds containing the groupings present in 2-amino thiazole and in isothiourea compounds. The concentrations of these organic sulfide compounds may be as low as 1 to 10 milligrams per liter, and in these concentrations extend the bright plating range obtained with obenzoyl sulfimide and the Class II (unsaturated compounds) brighteners down into very low current density areas.

United States Patent 1191 Brown et al.

[ 1 Apr. 8, 1975 I ELECTRODEPOSITION OF BRIGHT COBALT PLATE [73]Assignee: Oxy Metal Finishing Corporation,

Warren, Mich.

[22] Filed: Aug. 1, 1973 [21] Appl. No.: 384,777

Related U.S. Application Data [63] Continuation-in-part of Ser. No.266,105. June 26. 1972, abandoned. which is a continuation-in-part ofSer. No. 869,334, Oct. 24, 1969, both abandoned.

6/1958 Gundel et al. 204/49 2.900.707 8/1959 Brown 204/49 X 2.921.8881/1960 Halpert 2,978,391 4/1961 DuRose 3.093.557 6/1963 Cope et a1204/43 T FOREIGN PATENTS OR APPLICATIONS 261.025 12/1962 Australia204/49 Primary. E.\'aminer-G. L. Kaplan Attorney, Agent, or Firm-B. F.Claeboe [57] ABSTRACT A method to extend the bright plating rangeobtained with o-benzoyl sulfimide as the principle Class I brightener inacidic cobalt plating baths containing at least 90 percent by weightcobalt down into the very low current density areas or recesses by theuse of bath-soluble organic sulfide compounds containing the groupingspresent in 2-amino thiazole and in isothiourea compounds. Theconcentrations of these organic sulfide compounds may be as low as l to10 milligrams per liter, and in these concentrations extend the brightplating range obtained with o-benzoyl sulfimide and the Class II(unsaturated compounds) brighteners down into very low current densityareas.

10 Claims, No Drawings ELECTRODEPOSITION OF BRIGHT COBALT PLATE CROSSREFERENCE TO RELATED CASES This application is a continuation-in-part ofApplication Ser. No. 266,105 filed June 26, 1972, which is in turn acontinuation-in-part of Application Ser. No.

869,334 filed Oct. 24, 1969, and both now abandoned.

This invention relates to the electrode position from aqueous acidicbaths of bright cobalt plate containing at least 90 percentby weightcobalt.

One object of this invention is to increase the bright plating range ofacidic bright cobalt plating baths that employ O-benzoyl sulfimide(Class I nickel brightener) and Class II nickel brighteners (unsaturatedorganic compounds) by making possible bright plating in recessed areaswhere the current densities may be about amp/sq.ft. and lower.

Another object is to provide means to increase the tolerance of brightacidic cobalt plating baths containing at least 90% by weight cobalt tolarger concentrations of copper, iron, chromic acid and zinc impuritieswhich cause darkish plating in the recesses or low current densityareas, and also to larger concentrations of Class II nickel brightenerswhich tend to cause dull or darkish plating in the low current densityareas in cobalt baths much more readily then they do in predominatelynickel baths.

These objects and others may be accomplished by the use in the bath oflow concentrations of one or more of the bathsoluble organic sulfidecompounds of the type given in Table I, in conjunction with o-benzoylsulfimide, one of the most effective of all Class I brighteners (seeTrans. Electrochem. Soc., Vol. 89. p.414. 1946). The compounds shown inTable I contain the grouping (A) I I2 R1- N I C S R3 where R is hydrogenor a carbon atom -of an organic radical, R is nitrogen or a carbon atomof an organic radical, and R is a carbon atom of an organic radical. Rand R or R, and R may be linked together through a single organicradical.

More specifically, the bath soluble organic sulfide compounds used are2-amino thiazoles and isothioureas having the formulae:

R1-CN (B) R--c C-NH-'R and m M U R n 6-H wherein R is selected from H,lower alkyl sulfonic acid groups, aryl sulfonic acid groups, loweralkoxy aryl sulfonic acid groups andthe salts thereof;

R and R are selected from H, halogen, and lower alkyl or alkoxy groups;

R is selected from lower alkyl sulfonic acid groups, aryl sulfonic acidgroups and lower alkyl carboxy acid groups, and the salts thereof; and

R is selected from H, halogen, and lower alkyl or alkoxy groups.

It is to be appreciated that in referring to halogens, it is intended toinclude chlorine, bromine, fluorine and iodine, although chlorine isgenerally preferred. Moreover, where reference is made to lower alkyl oralkoxy groups, it is intended to include groups containing from about 1to 6 carbon atoms in a straight or branched chain, with from about 1 to4 carbon atoms being preferred. Additionally, in referring to thesulfonic or carboxy acids and their salts, it is intended to includethose sulfonic and carboxyacids which have halogen substituents on theiralkyl, alkoxy or aryl groups, and wherein the salts are exemplified bythe alkali metal salts, sodium, potassium, lithium, cesium and rubidium,and particularly sodium.

With o-benzoyl sulfimide present in the acidic cobalt baths inconcentrations ranging from about 0.3 grams/- liter to saturationconcentrations of about 12 grams/- liter, as little as l to 5 mg/literof the Compounds of Table I are effective in clearing up and brighteningup the recessed areas or low current density areasfThe obenzoylsulfimide compounds used in conjunction with other well-known Class Ibrighteners such as benzene sulfonamide, o-sulfobenzaldehyde,.vinylsulfonic, beta sulfo-styrene, allyl sulfonic, vinyl benzene, sulfonicacid and the like and in conjunction with well-knownClass ll compoundssuch as bath-soluble unsaturated alco-zhols and glycols, unsaturatedether alcohols, and glycols, pyridines and quinolines, and other ClassII unsaty urated compounds while making possible bright ductile cobaltplate, nevertheless do not have as wide a bright plating range as thesebrighteners have in acidic nickel plating baths, and dull platefrequently results in the low current density areas. This is true evenwith lower bath temperatures than that customarily used for brightnickel plating, and also this is true even at the lower bath pH rangessuch as 2 to 3.5, even though these conditions otherwise allow thebroadest bright plate range. If benzene or toluene sulfinates (U.S. Pat.No. 2,654,703, Oct. 6, 1953) are also present in the cobalt platingbaths containing at least percent by weight cobalt, this sensitivity iseliminated. However, the main fault of these sulfinates is that they arereadily oxidized, especially when air agitation is used to obtainmaximum brightness and high current density operation. While theoxidation products are not harmful (benzene or toluene sulfonates areformed), nevertheless, the rapid depletion rate of the sulfinates makescontrol of the bright plating range of the cobalt plating baths lesssimple. On the other hand, the compounds exemplified in Table I, whilenot decreasing the sensitivity of the bright plating range as much asthe benzene and toluene sulfinates, especially when cathode-rod ormechanical solution agitation is used instead of air-agitation,nevertheless they are more stable under all bath conditions andtherefore are easier to control, and in airagitated cobalt baths are fareasier to control.

The very effective brightening in the low current density areas by thecompounds exemplified in Table I is very important in bright platingintricately shaped articles such as brass plumbing goods, copper orbrass plated zinc die castings, steel appliances and the like, wheredeep recesses must be plated bright in order to receive the subsequentthin chromium plate.

The compounds exemplified in Table l are preferably used in lowconcentrations of about 1 to 5 mg/liter in the baths containingo-benzoyl sulfimide, although in some instances concentrations as highas about mg/liter or higher may be used. It has been found that whenconcentrations higher than about 10 mg/liter are used, too much sulfidesulfer may be incorporated in the plate and this may cause poor ordecreased chromium coverage in the low current density areas during theelectrodeposition of the usual top thin chromium plate. In the straightacidic cobalt plating baths, however, higher concentrations to 50 mg/l)of the compounds of Table I do not cause poor chromium coverage of thecobalt plate in the low current density areas (recesses) as they do withthe bright plate from acidic nickel plating baths, nor do they decreasethe leveling as they do in bright nickel plating baths when the Class IInickel brighteners are present with obenzoyl sulfimide in the straightcobalt or high cobaltnickel alloy plating baths.

The Class I and Class II nickel brighteners (see Modern Electroplating,"p. 311 to p. 313. John Wiley and Sons, 1953, or the Second Edition, I963p. 272 and p. 273) as is well known (Trans. Electrochem. Soc., 1946,Vol. 89, p. 414) are more sensitive in acidic high chloride (above 150g/l NiCl .6I-I O) baths than in Watts high nickel sulfate baths. Forexample, benzene or naphthalene monodior tri-sulfonic acids are poorClass I brighteners in the high chloride baths and Class II compoundscooperate hardly at all with these benzene or naphthalene sulfonicacids. In the acidic all cobalt plating baths and in the highcobalt-nickel alloy plating baths, the Class I brighteners used togetherwith the Class II brighteners are even more sensitive than in the highchloride baths, and only one Class I brightener, o-benzoyl sulfimide(saccharin), is remarkably effective to give ductile bright levelingplate with Class II compounds as already pointed out (Trans. Electrochem. Soc., 1946, Vol. 89, p. 414, and in U.S. Pat. No. 2,654,703, Oct.6, I953, col. 1). Nevertheless, even with o-benzoyl sulfimide present inthe all cobalt or high cobalt alloy plating baths, as for example apercent cobalt- 10 percent nickel bath, the Class II brighteners aremore sensitive (dull areas) in the acidic cobalt plating baths, andlower bath temperatures of about 1 15-1 30F and lower bath pH values ofapproximately 2.5 to 3.5 must, in general, be used for the broadestbright plating range, and the compounds of Table I must be added toobtain bright very low current density areas under most conditions.Also, in the acidic nickel baths, naphthalene sulfonic acids give goodbrilliance with Class llbrighteners in high sulfate baths, but they donot accomplish this in high cobalt sulfate baths, and dullish plates areobtained instead. In the case of the acidic cobalt baths, o-benzoylsulfimide is the only effective Class I compound which gives highbrilliance and ductlity with Class II compounds, as was alreadyemphasized in the previous references.

Some of the compounds in Table I, such as examples (5) and (6), havebeen suggested in the U.S. Pat. No. 2,648,627 dated Aug. 11, 1953 foruse in nickel plating baths, especially in the Watts type, in order toobtain full bright deposits, and the lower limit of the concentration toaccomplish this was set at mg/liter and actually in the preferredexamples higher concentrations were suggested. In the present invention,however, significantly lower concentrations are used, and even thenthese compounds in low concentrations are not helpful unless oneparticular Class I compound is present, namely; o-benzoyl sulfimide. Infact, if 0- benzoyl sulfimide is not present, the Class II brightenersare of little value, and also most all of the Class 1 compounds are oflittle value from the standpoint of producing bright ductile levelingcobalt deposits. When they are present in concentrations above about 0.3g/l; and preferably in the range of2 to 12 g/l, then all of the Class Iand especially Class II brighteners make important contributions tobrightness and leveling. Nevertheless, the brighteners are moresensitive than in nickel baths, and the lower range of bath temperaturesand pH values mustbe used for the broadest bright plating ranges, andeven then in most cases, it is very helpful to use small concentrationsof the compounds exemplifled in Table I to maintain bright very lowcurrent density areas, especially in air-agitated acidic cobalt platingbaths.

TABLE I Concentration Range '(g'amsliter) NH2. s

a c-N'- H mom-0.04

TABLE I --Continued Compound (1), Z-aminothiazole and compound (2),2-aminobenzothiazole can be reacted with bromoethane sulfonate, propanesultone, benzyl chloride, dimethyl sulfate, diethyl sulfate, methylbromide, propargyl bromide, ethylene dibromide, allyl bromide, methylchloroacetate, sulfophenoxyethylene bromide, the latter, for example,can be reacted with compound l to give compound (3) to form compoundswhich give even more improved results over compounds (1) and (2). Also,substituted Z-aminothiazoles and 2- aminobenzothiazoles, such as2-amino-5- chlorothiazole, 2-amino-4-methylthiazole and the like can beused instead of compounds l and (2). To form compounds such as (5) and(6), thiourea can be reacted with propiolactone, butyrolactone,chloroacetic acid, chloropropionic acid, propane sultone, dimethylsulfate and the like. Also, phenyl thiourea, methyl thiourea, allylthiourea and other similar substituted thoureas may be used in thereactions to form compounds similar to types (5) and (6). With thehigher molecular weight compounds such as in examples (3) and (4),higher concentrations of these less critical compounds up to 40 mg/litercan be used for optimum results, whereas in general, only 1 to 5mg/liter are needed for optimum results and in some cases, 1 to 10mg/liter when the contamination of the baths with impurities such aschromic acid (over mg/liter) or zinc (over 30 mg/liter) or copper ions(over 5 mg/liter) are excessive. The compounds of Table I are by farmore effective in air-agitated acidic cobalt plating baths, and

generallyless effective where just cathode-rod agitation is employed.

Of the listed representative acidic cobalt plating baths, the acidichigh cobalt fluoborate as with nickel fluoborate baths does not allownearly as good leveling with the brighteners as the sulfate and chloridebaths or the mixed sulfate-chloride baths. At bath pH values below about2.5 the leveling falls off, but not as'rapidly as in nickel baths. Thelower the bath temperatures, the higher the possible pH range which canbe used without dulling setting in. The acidic cobalt plating baths,wherein the cobalt is at least 90 percent by weight, have higherlimiting cathode current densities without burning as compared to equalmetal ion concentration nickel baths, and therefore using lower bathtemperatures for the cobalt baths, for example, about 48 to 55C, stillallows at least as high cathode current densilties to be used as incomparable nickel baths operated at 60 to 65C.

O 0 0 l-O 0 l 20 RE l RESENTATlVE COBALT BATHS 1. CoSO,.7H O 100- 200g/l CoCl .6H O 0 50 g/l a n 20 60 g/l pH 2-5 Temp. Room to 55C C.D. upto 150 21mps/sq.ft. (l5 ampslsqdm.) 25 2. CoCl .6H O 100 200 g/l H-IBOSI20 80 g/l pH 2. Temp. Room to 55 C CD. up t() [50 amps/sq.ft. (l5ampslsqdm.)

3. COSOJH O I00 200 g/l H 80 40 80 g/l NaF 0.5 15 g]! CoCl .6H ,O l0 g/lpH 25 Temp. Room to 55C C.D. up to 150 amps/sq.ftv (l5 ampslsq.dm.) 4.Co(BF I00 200 g/l C0Cl .6H-;O l0 40 g/l H BO l0 40 g/l pH 2.5-5.5 Temp.Room to 55 C 35 CD. up to 200 amps/sq.ft. (20 amps.sq.dm.)

5. C0(OSO NH lOO 300 g/l H BO 30 80 g/l pH 2.5-5 Temp. Room to 55C C.D.up to 200 ampslsqft. (20 amps.sq.dm.)

Below are two examples of bright cobalt plating baths.

(A) CoCl .6H O 100 g/l H3 60 al o-benzoyl sulfimide 2-6 g/l Allylsulfonic acid 8" lsothiourea-S-acetic acid (Compound 5, I Table l) 0.03g/l 2-butynoxyl ,4 diethane sulfonic acid (HO,-,SC-=H OCH C E C CH OCH,SO -,H) 0.1-6 g/l 2-butynel ,4-disulfonic acid 4 /l pH 2.5 to 3.5Temp. 50C Air-agitation CD. 50 amps/sq.ft.

(The sodium salts of the sulfonic acids may be used) (B) COSO .7H O lOOlSO g/l CoCl .6H O 0 30 g/l H 80 40 I g/l NaBF, 0.5 2 g/l o-benzosulfimide 2 l0 g/l Allyl su fonic acid 0.5 3 g/l 2-amino thiazole(Compound I of Table 60 I) 0.002 g/l HOC H OCH C E C-CH OC H,OH 0.02 0.5g/l In Example (B), use pH values of 2.5 to 3.8, temperature 50C, andCD. of 50 amps/sq.ft. If cathode-rod agitation is used, the higherconcentrations of brighteners are usually used compared toair-agitation. In all sulfate acidic plating bath containing dissolvedtherein obenzoyl sulfimide in a concentraton of about 0.3 grams perliter to saturation and additionally an organic sulfide compound in aconcentration of from about 1 to 40 milligrams per liter which compoundcontains the grouping wherein R is selected from H, halogen and loweralkyl or alkoxy groups, and R is selected from lower alkyl sulfonic acidgroups, aryl sulfonic acid groups, and lower alkyl carboxy acid groupsand the salts thereof, the lower alkyl carboxy acids and sulfonic acidsare defined as those containing 1 to 6 carbon atoms in a straight orbranched chain.

2. A bath for electrodepositing a bright cobalt plate upon a substrate,comprising an aqueous acidic plating bath fordepositing said cobaltplate upon said substrate said bath having dissolved therein o-benzoylsulfimide in a concentration of about 0.3 grams per liter to saturationand additionally an organic sulfide compound in a concentration of fromabout 1 to 40 milligrams per liter which compound contains the grouping:

C-S--R wherein R is selected from H, halogen and lower alkyl or alkoxygroups, and R is selected from lower alkyl sulfonic groups, arylsulfonic acid groups and lower alkyl carboxy acid groups and the saltsthereof, the lower alkyl carboxy acids and sulfonic acids as well aslower alkyl and alkoxy groups are defined as those containing l to 6carbon atoms in astraight or branched chain.

3. A bath for electrodepositing a bright cobalt plate upon a substrate,comprising an aqueous acidic plating bath for depositing said cobaltplate upon said substrate, said bath having dissolved therein o-benzylsulfimide in a concentration of about 0.3 grams per liter to saturationand additionally an organic sulfide compound in a concentration of fromabout 1 to 40 milligrams per liter, in which the organic sulfidecompound has the formulae:

R CN ll ll R C C- NH- R and c s R R- N 7 wherein R is selected from H,lower alkyl sulfonic acid groups, aryl sulfonic acid groups, loweralkoxy aryl sulfonic acid groups and the salts thereof;

R and R are selected from H, halogen, and lower alkyl groups;

R is selected from lower alkyl sulfonic acid groups and lower alkylcarboxy acid groups and the salts thereof; and

R is selected from H, halogen, and lower alkyl groups.

4. A bath as claimed in claim 3, wherein the organic sulfide compound isZ-amino-thiazole in a concentration of about 1 to about 14 milligramsper liter.

5. A bath as claimed in claim 3, wherein the organic sulfide compound isisothiourea-S-propionic acidin a concentration of about 1 to 10milligrams per liter.

6. A bath as claimed in claim 3, wherein the organic sulfide compound isHC- I H ill Ll c in a concentration of 1 to 40 milligrams per liter.

- 7. A method for depositing bright cobalt plate, comprising the step ofelectrodepositing said metal plate from an aqueous acidic plating bathcontaining dissolved therein o-benzyl sulfimide in a concentration ofabout 0.3 grams per liter to saturation and additionally an organicsulfide compound in a concentration of from about 1 to 40 milligrams perliter in which the organic sulfide compound has the formulae:

and;

wherein R is selected from H, lower alkyl sulfonic acid groups, arylsulfonic acid groups, lower alkoxy aryl sulfonic acid groups and thesalts thereof;

R and R are selected from H, halogen, and lower 10. A method as claimedin claim 7, wherein the oralkyl groups; ganic sulfide compound is R isselected from lower alkyl sulfonic acid groups and lower alkyl carboxyacid groups and the slats thereof; and R is selected from H, halogen,and 5 lower alkyl groups. I 8. A method as claimed in claim 7, whereinthe or- HQ C c 14 M ganic sulfide compound is Z-amino-thiazole in aconcentration of about 1 to about 10 milligrams per liter. 5

9. A method as claimed in claim 7, wherein the organic sulfide compoundis isothiourea-S-propionic acid in a concentration of about 1 to about10 milligrams in a concentration of l to 10 milligrams per liter. perliter.

1. A method for electrodepositing a bright cobalt plate upon a substratecomprising the step of electrodepositing said plate upon said substratefrom an aqueous acidic plating bath containing dissolved thereino-benzoyl sulfimide in a concentraton of about 0.3 grams per liter tosaturation and additionally an organic sulfide compound in aconcentration of from about 1 to 40 milligrams per liter which compoundcontains the grouping
 2. A BATH FOR ELECTRODEPOSITING A BRIGHT COBALTPLATE UPON A SUBSTRATE, COMPRISING AN AQUEOUS ACIDIC PLATING BATH FORDEPOSITING SAID COBALT PLATE UPON SAID SUBSTRATE SAID BATH HAVINGDISSOLVED THEREIN -BENZOYL SULFIMIDE IN A CONCENTRATION OF ABOUT 0.3GRAMS PER LITER TO SATURATION AND ADDITIONALLY AN ORGANIC SULFIDECOMPOUND IN A CONCENTRATION OF FROM ABOUT 1 TO 40 MILLIGRAMS PER LITERWHICH COMPOUND CONTAINS THE GROUPING:
 2. The process of claim 1 in which.beta.-alkenyl halides are converted to .alpha., 68 -dienes.
 3. A BATHFOR ELECTRODEPOSITING A BRIGHT COBALT PLATE UPON A SUBSTRATE, COMPRISINGAN AQUEOUS ACIDIC PLATING BATH FOR DE POSITING SAID COBALT PLATE UPONSAID SUBSTRATE, SAID BATH HAVING DISSOLVED THEREIN O-BENZYL SULFIMIDE INA CONCENTRATION OF FROM A ABOUT 0.3 GRAMS PER LITER TO SATURATION ANDADDITIONALLY AN ORGANIC SULFIDE COMPOUND IN A CONCENTRATION OF FROMABOUT 1 TO 40 MILLIGRAMS PER LITER, IN WHICH THE ORGANIC SULFIDECOMPOUND HAS THE FORMULAE:
 3. The process of claim 1 in which allylhalide is converted to 1,5-hexadiene.
 4. A bath as claimed in claim 3,wherein the organic sulfide compound is 2-amino-thiazole in aconcentration of about 1 to about 14 milligrams per liter.
 4. Theprocess of claim 1 in which allyl halide is electrolyzed in a dividedcell in a catholyte containing a supporting electrolyte salt and anon-aqueous solvent and 1,5-hexadiene is obtained in a yield of at least75% based on current efficiency.
 5. The process of claim 4 in which thecathode potential is such that a predominant amount of the allyl halideis reduced by taking up two electrons.
 5. A bath as claimed in claim 3,wherein the organic sulfide compound is isothiourea-S-propionic acid ina concentration of about 1 to 10 milligrams per liter.
 6. A bath asclaimed in claim 3, wherein the organic sulfide compound is
 6. Theprocess of claim 4 in which the allyl halide is allyl chloride and somebromide salt is provided in the catholyte.
 7. The process of claim 4 inwhich the allyl halides electrolyzed in an electrolysis mediumconsisting of a solvent having a dielectric constant of at least 50 anda quaternary ammonium salt.
 7. A method for depositing bright cobaltplate, comprising the step of electrodepositing said metal plate from anaqueous acidic plating bath containing dissolved therein o-benzylsulfimide in a concentration of about 0.3 grams per liter to saturationand additionally an organic sulfide compound in a concentration of fromabout 1 to 40 milligrams per liter in which the organic sulfide compoundhas the formulae:
 8. A method as claimed in claim 7, wherein the organicsulfide compound is 2-amino-thiazole in a concentration of about 1 toabout 10 milligrams per liter.
 8. The process of claim 4 in which thecathode voltage is more negative than -1.8 volts (vs. saturated calomelelectrode) and a quaternary ammonium salt is employed and there is atmost a very minor amount of reduction of the olefinic bonds in thereactant.
 9. The process of claim 8 in which a solvent is employedselected from the group consisting of dimethylformamide, acetonitrileand hexamethylphosphoromide, and the electrolysis is conducted atambient temperature.
 9. A method as claimed in claim 7, wherein theorganic sulfide compound is isothiourea-S-propionic acid in aconcentration of about 1 to about 10 milligrams per liter.
 10. A methodas claimed in claim 7, wherein the organic sulfide compound is
 10. Theprocess of claim 1 in which a quaternary ammonium salt is present assupporting electrolyte and a solvent is employed selected from the groupconsisting of dimethyl-formamide, acetonitrile andhexamethylphosphoramide.
 11. The process of claim 1 in which the halideis electrolyzed in a non-aqueous solvent having a dielectric constant ofat least 50 in the presence of a supporting electrolyte salt.
 12. Theprocess of claim 11 in which the supporting salt is a quaternaryammonium salt.
 13. The process of claim 1 in which the electrolysis isconducted in the absence of solvents which are proton donors.
 14. Theprocess of preparing 1,6-dibromohexane which comprises convertingpropylene to allyl chloride, electrolyzing the allyl chloride to obtain1,5-hexadiene, and hydrobrominating by non-Markownikoff addition ofhydrogen bromide, to obtain 1,6-dibromohexane is substantial absence ofisomers, and in which process the electrolyzing is conducted inaccordance with claim 1.